1. Field of the Invention
The present invention relates to an abnormality factor identification apparatus, and particularly, to an abnormality factor identification apparatus that isolates an abnormality factor based on a symptom of a fault.
2. Description of the Related Art
To sense or predict an abnormality including a fault in an industrial machine such as a machine tool or a robot, typically, a sensor that differently responds depending on the abnormality factor (e.g., a fault type or a fault site) is installed near a target site, and a detection value from the sensor is used to sense or predict an abnormality. However, it is difficult to install a sensor in a manner to selectively respond to only a specific abnormality. Such a sensor may often respond to an abnormality associated with another factor. Thus, there is a need for isolating an abnormality factor.
Conventional techniques have been known to isolate an abnormality factor in a machine using detection values from sensors. For example, Japanese Patent Laid-Open No. 2011-060076 discloses a technique that determines the state of an abnormality based on signals from a number of sensors and internal information from a numerically controlled apparatus to identify the cause of alarm sounding, and outputs indication and a control signal. Japanese Patent Laid-Open No. 10-228304 also discloses a technique that modifies the drive and mechanism model to improve the accuracy of abnormality sensing for abnormality determination that responds to changes in characteristics of a processing apparatus. In addition, Japanese Patent Laid-Open No. 07-234987 discloses a technique that, for ease of a diagnosis of a fault in a numerically controlled apparatus, displays presumed causes at the fault site, and the like, and changes the presumed cause probability database for each occurrence of a fault.
An abnormality factor may be isolated by, as disclosed in Japanese Patent Laid-Open No. 2011-060076, installing a sensor for each site of an industrial machine and identifying the abnormality factor based on the strength of the sensor responding. However, the minimum possible number of sensors are desirably installed for cost savings and ease of maintenance.
If details of a phenomenon occurring for each abnormality factor are known in advance, as disclosed in Japanese Patent Laid-Open No. 07-234987, the preliminary knowledge can be used to isolate an abnormality factor. Generally speaking, however, a fault rarely occurs in an industrial machine, and it is often difficult to gather knowledge about a machine abnormality caused by a fault. Furthermore, sensor observation values may often be significantly influenced by the machine installation environment and the individual difference. Any prepared preliminary knowledge often has to be modified for use depending on the sensor installation environment and the individual difference. Thus, it is desirable to use no preliminary knowledge about sensor observation values.